Paul Irish : 10 Things I Learned from the jQuery Source

(function() {})() simply means the function is going to execute itself right away. I always had trouble understaning the jquery statements. (function (window, undefined ) {})(window); . And the first paranthesis is optional!
(function(window,document,udefined){
})(this, document);
//setInterval is bad, because it doesn't wait for the doStuff function to finnish its business.
setInterval(function(){
doStuff();
},100);